Double-blinded randomization was performed as follows. The remaining 50 patients were randomly assigned to 1 of 2 groups depending on the additional dexmedetomidine. Randomization was performed with a computerized random-sequence generator by an independent nurse who prepared a syringe for added dexmedetomidine or saline according to the assignment. The patients and all the medical staff who participated in the operation were blinded of the assignment.